Electrical differential oil well drilling system



Feb. 25, 1936. 5. STAEGE 2,032.155

ELECTRICAL DIFFERENTIAL OIL WELL DRILLING SYSTEM Filed Jan. 6, 1933 "III, 7 III 4, WITNESSES: INVENTOR Q511 .%a Stephen A. St'aeye BY ATTORNEY will be apparent that Patented Feb. 25, 1936 UNI-TED STATES PATENT OFFICE ELECTRICAL DIFFERENTIAL OIL WELL DRILLING SYSTEM Pennsylvania Application January 6, 1933, Serial No. 650,401

BClaims.

"I am well apprised of the fact that various attempts have heretofore been made to control the hoisting motor of a rotary well drilling system as a function of the load variations on the motor driving the drill table as different types of earth strata are encountered. However, in previous devices the flexibility of the control fell short of expectations, and further the amount of equipment needed made the price of the installations prohibitive to the trade.

In working on the invention herein presented, I kept the prior art in mind, and one of the objects of my invention is the provision of a simple, practical, inexpensive and accurate system of control whereby the drilling motor cannot be overloaded, crooked holes are avoided, broken and twisted-off drill stems are prevented, and the drilling operation proceeds with the maximum speed at which a given formation canbe properly drilled.

It is also an object of my invention to limit both the torque on the drillmotor and the weight of the drill stem.

A further object of my invention is the provision of a control system where the hoist motor need only be of a capacity suiflcient to retrieve the drill stem during drilling at such a speed that a constant torque is maintained on the drill motor.

A still further object of my invention is to control the movement of the drill stem as a function of the speed of the drill motor.

Other objects and. advantages will become apparent from a study of the following specification when considered in conjunction with the accompanying drawing, in which the single figure is a diagrammatic illustration of -my control system as applied to a rotary drilling equipment.

Referring more particuiarly to the drawing, it I propose to use a woun'd rotor induction motor ii for driving the drill table I. The-drill table is cperatlvely secured to the drill stem 2 which operates in the well 3. Since the drilling equipment is a conventional rotary type, it is provided with a water supply pipe 4 for removing the drilling material at the bottomof the well and the stem is suitably supported by the link 5 and hook 6 through cable I from the crown block 8. The cable 1 is secured atsome fixed point 9 to the derrick and the other end of the cable is wound about the hoist drum ill.

The hoist drum i is arranged to be operated by a direct-currenttorque motor l2 which is directly connected in the armature circuit of a direct-current generator I: mounted on the shaft of an induction motor I4. A separate exciter I8 is provided for exciting itself and the generator and the motor I2. It will be apparent that the machines l3 and II are nothing more than a motor generator set for supplying energy to the torque motor l2, the motor I 4 being secured through suitable switches SW to the source of alternating current l5.

To properly control the torque of motor I! the 10 excitation of the generator I3 is varied as a function of the current drawn from the line by the wound rotor induction motor II and as a consequence, the weight of the drill stem supportson the bottom of the well ismaintained substantially constant in a manner described more in detail hereinafter.

Probably a better understanding of my invention can be had by studying a sequence of operation for starting the drilling equipment and for normal drilling.

Assuming conductors I5, representing the source of alternating-current power, are suitably energized, the motor will thus operate, driving the generator I3 and the exciter l6. Since the circuit for the wound rotor induction motor is still open at the contact members 33, 34 and 35,

. the field winding of the generator i3 is not envergized and the generator l3 supplies energy of relatively small voltage to the motor l2. The 30 motor 12 tends to hoist the drill stem 2 from the well by a torque which is determined by the voltage of the generator !3 and excitation of the field 25 of the motor l2.

Since theexciter I6 is operating, the buses i9 5 and 20 are energized and the exciter field I1 is thus suitably self-excited through rheostat l8. Further, the generator I3 is excited to a predetermined degree by the field winding 2| through rheostat 22. The motor l2 .has its field winding 25 also excited through conductor 23, rheostat 24, resistor 26, to the bus i 9. If now the controller 32 be moved in the direction indicated by the arrow to the first controller position a, contact members 33, 34 and 35 are bridged by the controller segments 36, 31 and 38, respectively, thereby'energizing the primary winding 43 of the motor i l through conductors 40, 4| and 42. For the first controller position all of the resistors 44, 45 and 46 are in the secondary cir- 50 cult of the motor H and in consequence, a large starting torque is provided for the drill motor. Further, since a, large current fiows to the motor II, the current transformer 28 supplies considerable current to the field winding 30 through the rectifiers29. This current may act cumulative or difierential to the series field winding 3i, depending on the torque characteristics requiredfor motor l2. The voltage of the generator I3 is thus very materially'increased and the drill stem is retrieved sufiiciently to permit starting of the drill stern, regardless of the length of the stem, or the depth of the well.

As the controller 32 is moved to positions I), c and'd, respectively, theresistor sections 46, 45 and 44 are successively shunted and for normal drill operation, the induction motor I l operates as a squirrel cage induction motor.

As the character of the strata being drilled varies from time to time, the load on the drill the generator I3 is thus considerably increased.

The torque motor I2, having substantially constant excitation, will thus retrieve the drill stem sufiiciently to maintain a substantially constant torque on the drill motor II. If, on the other hand, the torque on the drill stem decreases, the

effect of field winding 30 decreases and in consequence, the weight of the drill stem 2, resting on the strata being drilled, is increased, so that again the torque on motor i I is maintained substantially constant. For'eachs length of the drill stem, and depending upon the size of the drill motor as well as the size of the hoisting motor, the rheostat 53 may need to be adjusted for the initial operating torque. After the adjustment for a. given length of drill stein has been. made,

no further adjustments need be made, because the current transformer operating through the rectifiers 29 suitably controls the voltage of the generator [3 to either retrieve the drill stein or permitthe drill stem to descend. This system 'will thus regulate for both torque on the drill motor as well as for the weight of the drill stem.

Further, with this arrangement the feed motor will only need to be of such size as is necessary to retrieve the drill at asatisfactory rate of speed forsuitable control, since current will be furnished to the armature of the hoist motor by'the small motor generator set, represented by the machines l4 and I3, the voltage of the generator of which is automatically being adjusted to give the proper torque for the motor l2. The motor l2 will thus at all times be-v responsive to the torqueof the drilling motor driving the rotary table I.

It will be seen-that any change in load on the drilling motor will cause acorresponding change in the current and field excitation of the variage voltage generator l3 and, therefore; a c e in voltage impressed upon the armature of the feed motor which will vary its torque 'so as to maintain substantially constant torque on the drill motor, and constant weight on' the drill stem.

The switch 21 is provided for the purpose. of shunting the resistor 26, whereby the motor I! is provided with a strong field excitation so that if the drill stem for any reason has gotten stuck,'

If the load increases, as is.

that other systems falling within the spirit of this invention and within the scope of the appended claims may readily be devised by those skilled in the art, after having had thebenefit .of the teachings of this invention, but I wish 5 the drill motor for varying'the voltage of the generator energizing the hoist motor.'

2. In a rotary well-drilling system, in combination, a drill stem, a drill table for operating the stem, a motor for driving the table, a hoist- 20 drum for lowering and retrieving the stem, a. torque motor for operating the hoist-drum, a generator for supplying energy to the torque motor, means for varying the voltage of said generator proportionally to the variations in torque 25 of the motor operating the drill table, whereby the stem is retrieved and lowered by an amount sufficient to maintain substantially constant torque on the motor operating the drill table.

3. In a rotaryw'ell drilling system, in com- 30 bination, a drill stem, a drill table, an induction motor for driving the drill table, a hoist-drum, a hoist motor for operating the hoist-drum, a motor-generator set for energizing said hoist motor, means responsive to the torque of the induction motor for controlling the operating characteristics of the motor-generator set so that the energy supplied to the hoist motor keeps a constant torque on the drill motor.

4. In a rotary well-drilling system, in com- 40 bination, a drill stem, a drill table for operating the stem, a drill motor for operating the table, a hoist motor for controlling the weight of the drill stem on the bottom of the well, a motor-generator set for energizing the hoist 'motor, means responsive to the load current of the drill motor for varying the operating characteristics of the motor-generator set to thus maintain the weight of the drill-stem on the bottom of the well substantially constant.

. 5. In a well-drilling system, in combination, a motor for operating the drilling tool, a hoist drum and hoist motor for'operating the drum, a motorgenerator set for energizing the hoist motor, and

means responsive to the torque of the motor for of said stem, a generator connected in series cir- F cuit relation with the torque motor, a motor for driving the generator at substantially constant speed, excitationcontrol means for the generator, said means including a device responsive to the load current .01 the drill motor whereby the voltage ofthe generator is controlled to be directly proportional-to said load current and the torque on the drill motor is thus maintained constant.

7. ma well drilling system,- 'in combination, a

. drilhtbol; a motor for operating the tool, a hoistenergized proportional to the load current of the motor, a. rectifier interconnected with the secondary winding of the transformer, a generator having a field winding, said field winding being supplied with energy from said rectifier whereby the voltage of the generator is directly proportional to the load current of the alternating cur= rent motor, a. constant-excited motor interconnected with said generator, and a hoist-drum for the drill stem driven by said constant-excited motor.

STEPHEN A; STAEGE. 

